As part of a well completion process, cased-holes/wellbores are perforated to allow fluid or gas from rock formations (reservoir zones) to flow into the wellbore. Perforating gun string assemblies are conveyed into vertical, deviated or horizontal wellbores, which may include cemented-in casing pipes and other tubulars, by slickline, wireline or tubing conveyance perforating (TCP) mechanisms, and the perforating guns are fired to create openings/perforations in the casings and/or liners, as well as in surrounding formation zones. Such formation zones may include subterranean oil and gas shale formations, sandstone formations, and/or carbonate formations.
Often, shaped charges are used to form the perforations within the wellbore. These shaped charges, serve to focus ballistic energy onto a target, thereby producing a round perforation hole (in the case of conical shaped charges) or a slot-shaped/linear perforation (in the case of slot shaped charges) in, for example, a steel casing pipe or tubing, a cement sheath and/or a surrounding geological formation. In order to make these perforations, shaped charges typically include an explosive/energetic material positioned in a cavity of a housing (i.e. a shaped charge case), with or without a liner positioned therein. It should be recognized that the case or housing of the shaped charge is distinguished from the casing of the wellbore, which is placed in the wellbore after the drilling process and may be cemented in place in order to stabilize the borehole prior to perforating the surrounding formations. Often, the explosive materials positioned in the cavity of the shaped charge case are selected so that they have a high detonation velocity and pressure. When the shaped charges are initiated, the explosive material detonates and creates a detonation wave, which will generally cause the liner (when used) to collapse and be ejected/expelled from the shaped charge, thereby producing a forward moving perforating material jet that moves at a high velocity. The perforating jet travels through an open end of the shaped charge case which houses the explosive charge, and serves to pierce the perforating gun body, casing pipe or tubular and surrounding cement layer, and forms a cylindrical/conical tunnel in the surrounding target geological formation.
Typically, liners include various powdered metallic and non-metallic materials and/or powdered metal alloys, and binders, selected to generate a high-energy output or jet velocity upon detonation and create enlarged hole (commonly referred to as “big hole”) or deep penetration (“DP”) perforations. These liners, however, may leave undesirable slugs/residuals of the liner material in the perforation tunnel, which may reduce and/or block flow of the fluid/gas in the perforation tunnel. Additionally, the perforating jet formed by typical liners may form a crushed zone (i.e., perforation skin, or layer of crushed rock between the round perforation/slot-shaped perforation tunnel and the reservoirs) in the surrounding formation, which reduces the permeability of the surrounding formation and, in turn, limits the eventual flow of oil/gas from the reservoir.
Liners having high quantities of tungsten are known, which may help to increase the depth of the perforation tunnel formed upon detonation of shaped charges, as exemplified in U.S. Pat. No. 5,567,906. A disadvantage of these liners is that in order to create a deep penetrating perforation the shaped charge jet may be extremely narrow in geometry and require a large quantity of high density powdered metallic materials.
Efforts to reduce slug formation, further clear the perforation tunnel, and/or remove the crushed zone have included the use of reactive liners. Such reactive liners are typically made of a plurality of reactive metals that create an exothermic reaction upon detonation of the shaped charge in which they are utilized. Powdered metallic materials often used by the reactive liners include one or more of lead, copper, aluminum, nickel, tungsten, bronze and alloys thereof. Such liners are, for instance, described in U.S. Pat. No. 3,235,005, U.S. Pat. No. 3,675,575, U.S. Pat. No. 8,075,715, U.S. Pat. No. 8,220,394, U.S. Pat. No. 8,544,563 and DE Patent Application Publication No. DE102005059934. Some of these powdered metallic materials may be heterogeneous or non-uniformly distributed in the liner, which may lead to reduced performance and/or non-geometric perforation holes. Another common disadvantage of these liners is that they may not be able to sufficiently reduce slug formation, clear the perforation tunnel, and/or remove the crush zone formed following detonation of the shaped charge.
Some metallic liner materials include powdered metallic materials having grain sizes that are less than 50 micrometers in diameter, while others may include larger grain sizes. Difficulty mixing the metals during the liner formation process may result in imprecise or inhomogeneous individual liner compositions with heterogeneous areas, (e.g., areas where the liner composition is predominantly a single element, rather than a uniform blend), within the liner structure. Efforts to improve mass producability of liners are sometimes met with compromised performance of the liners.
In view of the disadvantages associated with currently available methods and devices for perforating wellbores using shaped charges, there is a need for a device and method that provides a composition including metal powders for use in a shaped charge liner that is capable of generating an energy sufficient to initiate an exothermic reaction upon detonation of the shaped charge. Additionally, there is a need for shaped charge liners capable of forming an exothermic reaction to generate a thermal energy that creates a uniform perforating jet. Further, there is a need for a liner and/or a shaped charge including a liner, having a homogenous composition of metal powders having distinct grain size ranges. Finally, there is a need for a shaped charge liner in which its components allow for a more effective perforating jet, without adding significantly to overall shaped charge costs.